Neutron-rich fluorine isotopes lie near or on the southern shore of the IOI.
In recent years, a series of experiments had been conducted on these isotopes to explore the impact of intruder states
on their single-particle levels [1]}, [2]}, [3]}, [4]}, [5]}, [6]}, [7]}, [8]}.
In particular, the isotope \(^{28}\) F present an interesting situation.
It was found to be unbound with respect to neutron emission by Schiller et al. [2]}
from its relatively low upper limit for production in the reaction products of a secondary beam of \(^{29}\) Ne.
Later, using invariant mass spectroscopy,
Christian et al. [4]}, [5]} determined the ground state of \(^{28}\) F to be a resonance at 220(50) keV above the ground state of \(^{27}\) F,
is in good agreement with the USDA/USDB shell model predictions [12]},
suggesting that \(pf\)  shell intruder configurations play a minor role in the structure of the ground state of \(^{28}\) F,
even though calculations using the sdpf-u-mix interaction [13]} predict several low-lying negative parity states.
